全新java初学者实践教程6(Java SE5.0版)
32ae? d 基本语法3
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#^Jy#) 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
7{:g|dX 5N4[hQrVJ [font="Times] 1.循环语句[font="Times]:while,do-while,for
B^sHFc""V Zfn390 _ [font="Times]2.分支语句[font="Times]:if-else,switch,
(VA:`pstP [font="Times]
'P5|[du+ 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
7]6HXR @ [font="Times]
Hxzdxwz%$ 4.异常处理语句[font="Times]:try-catch-finally,throw
hg=BXe4: Il9pL~u 实践:
13:0%IO [font="Times] 1.循环语句
1F_ 1bAh$ [font="Times] while 语句
B)`^/^7 [font="Times]class While {
:i_kA'dl& [font="Times]public static void main(String args[]) {
/o=,\kM [font="Times]int n = 10;
FI|@=l;_ [font="Times]while(n > 0) {
KV$J*B Y [font="Times]System.out.println("tick " + n);
(6Sf#M [font="Times]n--;
o4g<[X) [font="Times]}
Uv"GG:
K_ [font="Times]}
MOEB{~v`; [font="Times]}
!rMl" Y[ [font="Times] do…while 语句
Cq, hzi- [font="Times] class DoWhile {
>{]mN5 [font="Times]public static void main(String args[]) {
qg;fh]j% [font="Times]int n = 10;
%<Q?|} [font="Times]do {
Bz#K_S [font="Times]System.out.println("tick " + n);
n\Y|0\ B [font="Times]n--;
%7oB[2 [font="Times]} while(n > 0);
C4ut!I # [font="Times]}
-j 6U{l [font="Times]}
)!``P?3? 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
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[font="Times] for语句
Ghgo"-,# [font="Times] class ForTick {
!B_?_ a [font="Times]public static void main(String args[]) {
4f?Y'+>Z, [font="Times]int n;
+=bGrn>h [font="Times]for(n=10; n>0; n--)
`+(|$?C u [font="Times]System.out.println("tick " + n);
GL_a`.=@ [font="Times]}
~CB6+t> [font="Times]}
boR&'yX 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
d#9"_{P 还有啊,[font="Times]for循环的部分可以为空的
y`EcBf [font="Times]class ForVar {
a+CHrnU\; [font="Times]public static void main(String args[]) {
$*{$90Q [font="Times]int i;
i-EFq@xl [font="Times]boolean done = false;
F"-w [font="Times]i = 0;
@9QtK69 [font="Times]for( ; !done; ) {
Bjz\L0d [font="Times]System.out.println("i is " + i);
s2@}01QPo [font="Times]if(i == 10) done = true;
_~`\TS8 [font="Times]i++;
NgnHo\) [font="Times]}
*L9s7RR [font="Times]}
bTn7$EG [font="Times]}
循环语句的例子下载 L:y}
L [font="Times] 2.分支语句[font="Times]
syYg, G[ [font="Times] if/else语句
)oSUhU26} [font="Times]class IfElse {
3 9Ql|l$ [font="Times]public static void main(String args[]) {
fFfH9 cl! [font="Times]int month = 4; // April
rwlV\BU [font="Times]String season;
AVR9G^ce_ [font="Times]if(month == 12 || month == 1 || month == 2)
Odr@9MJ [font="Times]season = "Winter";
Upr:sB [font="Times]else if(month == 3 || month == 4 || month == 5)
61Nj&1Ze [font="Times]season = "Spring";
:I5]|pt [font="Times]else if(month == 6 || month == 7 || month == 8)
OT9\K_ [font="Times]season = "Summer";
!j)H!|R [font="Times]else if(month == 9 || month == 10 || month == 11)
lq$1CI [font="Times]season = "Autumn";
xi=qap=S^9 [font="Times]else
O\T [font="Times]season = "Bogus Month";
\"qXlTQ1_9 [font="Times]System.out.println("April is in the " + season + ".");
/AR;O4X+ [font="Times]}
q($lL~Ls [font="Times]}
JqO#W1h~R| [font="Times]//这段程序输出[font="Times]:
8IH&=3 [font="Times]//April is in the Spring.
gkuI!= [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
+SmcZ^\OZ [font="Times] switch语句
byv(:xk|'e [font="Times] class Switch {
HlB'yOHv! [font="Times]public static void main(String args[]) {
D4m2*%M [font="Times]int month = 4;
>,` /
z [font="Times]String season;
Tv0|e'^ [font="Times]switch (month) {
z+1#p.F$@ [font="Times]case 12:
9BGPq) # [font="Times]case 1:
Jr18faEZw [font="Times]case 2:
~$f+]7 [font="Times]season = "Winter";
'!!w|kd [font="Times]break;
*_$%Tv.] [font="Times]case 3:
buRXzSR [font="Times]case 4:
)Xa`LG=| [font="Times]case 5:
X9nt;A2TU+ [font="Times]season = "Spring";
<GShm~XD2 [font="Times]break;
qoMYiF}/e [font="Times]case 6:
DFs
J}`
$ [font="Times]case 7:
uKqN [font="Times]case 8:
";j/k9DE [font="Times]season = "Summer";
M"K$81 [font="Times]break;
aT F} [font="Times]case 9:
QzIK580%t [font="Times]case 10:
4T6dju [font="Times]case 11:
}Xs=x6Mj [font="Times]season = "Autumn";
g?M\Z"; [font="Times]break;
$.(>Sj1 [font="Times]default:
pN&Dpz^ [font="Times]season = "Bogus Month";
3skq%;%Wsk [font="Times]}
TeQWrms [font="Times]System.out.println("April is in the " + season + ".");
BpCzmU [font="Times]}
PDX^MYoN [font="Times]}
分支语句代码下载 O!sZMGF$p .*D~ .! [font="Times]switch语句适合于条件非常多的逻辑
E/ (:\Cm^ 请看上述语句可以混合使用,请看
下载例子